My lens is in a super graphic lensboard that is made up of two plates. The lens shifts slightly - both when you cock the shutter, and when it is tripped. I can find nothing to tighten to keep these two plates from shifting. Any ideas?

I've never heard of a lens board having two plates. Sounds like someone added one to act as a shim when the mount ring tightned fully left front/rear movement and that the lens threads or mount ring do not fit the hole completely. Suggest measuring thread diameter of the lens and of the mount ring coresponding area and search for a proper sized lens board.

Sounds like you have the 1/1000 shutter, where you twist the front shade to cock it. If so, the two piece lens board is part of the design and from the factory. I had one apart several years ago to repair the shutter blades. Unless you are comfortable repairing shutters, I would leave it alone or send it in for repair.